The present invention relates to a new and improved, highly efficient, impact drive rotatable sprinkler device which is capable of evenly distributing very low volumes of water over a large area and can be provided with means for readily adjusting the segment of a circle to be watered (arc of throw) without affecting the amount of water distributed over the selected area per unit time.
Ball driven impact sprinklers are well known and have been manufactured and sold for many years. They have not, however, been well accepted by consumers because of their relatively short life expectancies, high pressure losses, undependable speed of rotation, poor water distribution, and lack of flexibility and ease of adjustment. Several of these problems are primarily the result of the particular drive mechanisms employed in such devices. These drive mechanisms generally operate in the same manner. As water is directed to the drive chamber, it is channeled through very small angular openings which greatly restrict the flow while significantly increasing its velocity, resulting in very small high velocity streams of water which enter the drive chamber at an inclined angle, forming a water vortex within the drive chamber. The drive ball, which is free to move in any direction within the drive chamber, is placed into rotation by the water vortex. The centrifugal force of the rotating ball moves the ball to the outer diameter of the drive chamber. The force of the swirling water vortex within the chamber move the ball upwardly and around the chamber, building the ball's velocity to a maximum just before it reaches the rotary portion of the sprinkler head which extends down into the drive chamber. The ball then strikes a lug, moving the sprinkler head a small amount. The ball then loses velocity, falls back into the bottom of the drive chamber, and the cycle is repeated.
As these devices rely entirely on the force of the impact of the ball to drive the sprinkler about its axis of rotation, the size of the steel drive ball must be relatively large, on the order of one-half inch in diameter. The drive chamber must also be relatively large, on the order of 3.5 inches across, to accommodate such travel of the ball. The introduction of high velocity water into a relatively large chamber and the repeated vertical lifting and dropping of the drive ball creates a large pressure drop across the sprinkler. In addition, the continued lifting and dropping of the ball within the chamber causes significant and rapid wear on the interior of the sprinkler. The result is an efficient drive mechanism and a short sprinkler life.
In addition to the problems resulting from the drive mechanisms in ball impact drive sprinklers, such devices have also suffered in performance as a result of this poor seal designs. The means for sealing such drive mechanisms are continuously subject to imbalance by reason of the force of the water spraying from only one side of the sprinkler. This imbalance is greatly exacerbated if one were to press downwardly on the sprinkler head during use. The uneven forces acting on the sprinkler seals tend to open the seals about the central axis of the sprinkler, creating leakage problems and allowing foreign matter to pass therein which adversely affects the rotation and thus the water distribution and life of the sprinkler.
On those ball impact drive sprinklers having means for presetting the arc of throw, not only are they difficult to adjust, requiring the use of tools and often additional parts, but there is generally no means to vary the volume of flow through the sprinkler to correspond with the preset arc of throw. As a result, a sprinkler which is spraying over a 90.degree. arc of throw would cover that area with four times the amount of water in a given amount of time as the same sprinkler dispersing water over 360.degree.. This results in uneven water coverage when different sprinklers in a sprinkler line are preset to different arcs of throw. In addition, the means for presetting the arc of throw in such sprinklers are very susceptible to damage. Such devices generally do not include clutch mechanisms. If one were to manually rotate the nozzle head of the sprinkler with respect to the sprinkler body, the impacting lugs which control the arc of throw and would be easily damaged. The present invention is directed to solutions to these problems while maintaining the economy of ball impact drive sprinklers.
To improve the efficiency and longevity of the drive mechanism, the present invention does not utilize high velocity jets of water to create a vortex for lifting, rotating and dropping the drive ball about and within a large drive chamber. Instead, a smaller and lighter drive ball is confined to a tight annular track about a small drive chamber, shaped to fit the ball. The ball is propelled about the track by three or more relatively low velocity streams of water which enter the drive chamber at an angle substantially tangential to the direction of travel of the ball. The formation of the low velocity streams does not sufficiently restrict the flow of water through the sprinkler so as to create an excessive pressure loss. The ball impact surfaces for the sprinkler are formed in the wall of the ball track and are shaped so as to fit the ball, allowing the rotating ball to impact and roll over the impact surfaces thereby greatly reducing the amount of wear in comparison to that heretofore experienced with vortex flow drive mechanisms. The impact surfaces also deflect the tangential water streams applying further rotary torque to the wall of the ball track. While the torque created by the impacting water alone is insufficient to rotate the track, the additional torque imparted by the impacting ball rotates the drive track an incremental amount with each impact, thereby effecting the desired slow rotation of the drive chamber which carries the rotary section of the sprinkler. As a result of this new configuration of ball track and drive chamber and by more efficiently utilizing the water flow through the drive chamber and maintaining uniform water flow from the water streams about the track and out the sprinkler nozzle, the need for high velocity water jets and the creation of a water vortex is eliminated, dramatically improving the efficiency and life of the sprinkler.
In addition to the improved drive mechanism, the present invention also employs a novel, pre-loaded seal assembly which not only protects the bearing surfaces from the intrusion of foreign matter, but also controls the bearing friction between the rotating and stationary sprinkler parts. This seal assembly comprises a plurality of stacked bearing and seal washers which are spring biased so as to evenly distribute the loading forces acting thereon and thus continuously maintain the desired bearing friction and eliminate the aforesaid seal separation problem even in those most severe instances where the sprinkler is subjected to a downward vertical force during use. In different embodiments of the present invention, means are provided for adjusting the arc of throw of the sprinkler so that the sprinkler will cover only a preset area. Not only is such means readily adjustable without the need for separate tools or additional parts, but includes cooperating means for varying the flow of water through the sprinkler so as to provide continuously uniform water coverage per unit time regardless of the preset arc of throw. Additionally, a clutch assembly is provided for allowing the sprinkler head to be manually rotated with respect to the sprinkler body without damaging the direction control mechanism and while maintaining the preset arc of throw. As will become apparent, the impact ball drive sprinkler disclosed herein overcomes each of the shortcomings heretofore experienced with such devices while maintaining the economic advantages of the ball drive mechanism.